CHEVY WHO HAS A MIND OF ITS OWN, HELP.

1996 Chevrolet Lumina • 6 cylinder 2WD Automatic • 202 miles

I have a 1996 chevy lumina 3.1L. It keeps dropping real low in idle and stalling out. When it does this is smells really bad of gas. It was also running real rough at times. It said codes: P1200 injector control circuit fault, P0300 engine misfire, P0341CMP sensor out of range, P0401 Insufficent EGR flow. I have replaced the cam sensor, spark plugs, wires, and egr valve. The coils are all firing, and so are the injectors. It took away the roughness but still randomly drops in idle and misfires like crazy. The egr valve was even bypassed and still does the same.I dont get it. My brother has tested everything he can think of and spent two days working on it and one minute its running perfect and next its droping and stalls out. Also I forgot to mention this only started after I had replaced my intake manifold that was leaking. Any suggestions or ideas? The computer? Injector randomly staying part way open? Please help so tired of not knowing when im gonna get brokedown again.

As far as idle, I clean the throttle-body and check the iac/idle air control. Intermittent isuues can be hard to track, you have to test when the problem is ongoing. If your dropping a cylinder, do a cylinder balance test, when the problem is ongoing. Killing a cylinder should have an effect on rpms, if you kill a cylinder that has no effect on rpms, start with that cylinder, it is either weak or dead. Spark--fuel compression? If you kill spark, do it quickly, so you don't flood anything.